The cyclic isomaltoligosaccharide is a cyclic oligosaccharide with 7 to 9 glucoses bound cyclically via .alpha.-1,6-linkages. The cyclic isomaltoligosaccharide has a hollow space in the molecule, and the inside of this hollow space, as similar to cyclic dextrin (hereinafter abbreviated as CD), is hydrophobic and thus has an inclusion action for incorporating various oily substances into it. Because of this action, application of the cyclic isomaltoligosaccharide is expected in the fields of food industry, chemical industry, pharmaceutical industry etc. Further, unlike CD, the cyclic isomaltoligosaccharide specifically inhibits the action of glucan synthase produced by cariogenic bacteria. As a result, formation of dental plaques as a cause for dental caries is significantly prevented, so application thereof as cariostatic agent is also expected.
Heretofore, nucleic acid analogues such as azidothymidine (AZT), dideoxyinosine (DDI) etc. which are inhibitors for reverse transcriptases transcribing retroviral RNA into DNA, as well as protease inhibitors derived from retroviruses, have been utilized for the purpose of preventing and treating retroviral diseases, particularly AIDS. However, nucleic acid analogs such as AZT etc., if administered for a long period of time, cause disorders in bone marrow or side effects such as acute pancreatitis and peripheral neuropathy or lead to generation of viruses resistant to these drugs. The protease inhibitors also suffer from the problem of generation of resistant viruses upon long-term administration. Therefore, treatment of AIDS etc. at present makes use of a combination of drugs each having different working mechanism, but there is nevertheless the problems of side effects upon long-term administration or the possibility of generation of new resistant viruses.
Meanwhile, in 1987, it was revealed that sulfated polysaccharides represented by dextran sulfate significantly inhibit the binding of AIDS virus to the CD4 receptor on the surface of T cells in a completely different mode of action to those of the above-described drugs. These sulfated polysaccharides are extremely low in cytotoxicity and inexpensive so their practical application was expected. However, these sulfated polysaccharides exhibited significant inhibitory activity in vitro but did not in vivo. The presumed reason is that they are hardly absorbed because of their high molecular weight or that the polysaccharides are subject to decomposition in a living body. A sulfated CD derivative appeared to compensate for this drawback. However, although this substance is absorbed relatively easily into a living body, there may be a problem with the strong hemolytic activity inherent in CD, so it is still not practical for use even now.